2443d832 (in 1.0.4) ensures that the repl doesn't overwrite `_`, but it
replaces the server's global `_` with shell-server's `_`. This changes
appears to preserve it.
Fixes#4010.
Fixes the bug where the history would be parsed as one big blob on Windows,
because it is always written with "\n" but parsed with "\r\n" on Windows and
"\n" on Unixy platforms.
Since this file ends up getting copied into the server bundle, along with
files like boot.js, it makes sense to keep it with those files.
Renamed tools/shell/client.js to tools/shell-client.js for symmetry.